Methods of this type are conventional and typically include active cooling and/or heating of the diode laser or the pump light source to stabilize the wavelength of the pump light for operation, which is a function of the temperature of the diode laser. The temperature control of the diode laser may be performed, for example, by Peltier elements or also by using a water cooling system. However, an effort of this type for temperature control of the diode laser is not cost-effective in many areas of application, in particular if the pump light source is used in the motor vehicle field.